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/*
* Copyright (c) 2014 Hauke Mehrtens <hauke@hauke-m.de>
*
* Backport functionality introduced in Linux 3.18.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/if_ether.h>
#include <linux/if_vlan.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <scsi/fc/fc_fcoe.h>
/**
* eth_get_headlen - determine the the length of header for an ethernet frame
* @data: pointer to start of frame
* @len: total length of frame
*
* Make a best effort attempt to pull the length for all of the headers for
* a given frame in a linear buffer.
*/
int eth_get_headlen(unsigned char *data, unsigned int max_len)
{
union {
unsigned char *network;
/* l2 headers */
struct ethhdr *eth;
struct vlan_hdr *vlan;
/* l3 headers */
struct iphdr *ipv4;
struct ipv6hdr *ipv6;
} hdr;
__be16 protocol;
u8 nexthdr = 0; /* default to not TCP */
u8 hlen;
/* this should never happen, but better safe than sorry */
if (max_len < ETH_HLEN)
return max_len;
/* initialize network frame pointer */
hdr.network = data;
/* set first protocol and move network header forward */
protocol = hdr.eth->h_proto;
hdr.network += ETH_HLEN;
/* handle any vlan tag if present */
if (protocol == htons(ETH_P_8021Q)) {
if ((hdr.network - data) > (max_len - VLAN_HLEN))
return max_len;
protocol = hdr.vlan->h_vlan_encapsulated_proto;
hdr.network += VLAN_HLEN;
}
/* handle L3 protocols */
if (protocol == htons(ETH_P_IP)) {
if ((hdr.network - data) > (max_len - sizeof(struct iphdr)))
return max_len;
/* access ihl as a u8 to avoid unaligned access on ia64 */
hlen = (hdr.network[0] & 0x0F) << 2;
/* verify hlen meets minimum size requirements */
if (hlen < sizeof(struct iphdr))
return hdr.network - data;
/* record next protocol if header is present */
if (!(hdr.ipv4->frag_off & htons(IP_OFFSET)))
nexthdr = hdr.ipv4->protocol;
} else if (protocol == htons(ETH_P_IPV6)) {
if ((hdr.network - data) > (max_len - sizeof(struct ipv6hdr)))
return max_len;
/* record next protocol */
nexthdr = hdr.ipv6->nexthdr;
hlen = sizeof(struct ipv6hdr);
} else if (protocol == htons(ETH_P_FCOE)) {
if ((hdr.network - data) > (max_len - FCOE_HEADER_LEN))
return max_len;
hlen = FCOE_HEADER_LEN;
} else {
return hdr.network - data;
}
/* relocate pointer to start of L4 header */
hdr.network += hlen;
/* finally sort out TCP/UDP */
if (nexthdr == IPPROTO_TCP) {
if ((hdr.network - data) > (max_len - sizeof(struct tcphdr)))
return max_len;
/* access doff as a u8 to avoid unaligned access on ia64 */
hlen = (hdr.network[12] & 0xF0) >> 2;
/* verify hlen meets minimum size requirements */
if (hlen < sizeof(struct tcphdr))
return hdr.network - data;
hdr.network += hlen;
} else if (nexthdr == IPPROTO_UDP) {
if ((hdr.network - data) > (max_len - sizeof(struct udphdr)))
return max_len;
hdr.network += sizeof(struct udphdr);
}
/*
* If everything has gone correctly hdr.network should be the
* data section of the packet and will be the end of the header.
* If not then it probably represents the end of the last recognized
* header.
*/
if ((hdr.network - data) < max_len)
return hdr.network - data;
else
return max_len;
}
EXPORT_SYMBOL_GPL(eth_get_headlen);
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